This invention pertains to orthodontic headgear, and more particularly to a safety-release tension-applying mechanism for use between an orthodontic facebow and a headstrap and the like therefor.
It is common in certain orthodonture practices to use what is known as a facebow for applying certain tooth-positioning and/or mouth-positioning forces. The usual facebow includes an inner bow which seats in tubes, or other suitable devices, mounted on bands which have been attached to a patient's teeth, and an outer bow which is attached to the inner bow, and which extends around the opposite sides of the patient'face. Tension is applied, ordinarily, through an elastic neckstrap or headstrap, or the like, whose opposite ends hook with the opposite ends of the outer bow in a facebow.
There have been a number of incidents in the past where, either accidentally or intentionally, a facebow is pulled forwardly away from a patient's face and then released. This situation produces a very dangerous slingshot effect when the facebow shoots back at a patient's face. Serious accidents, including blinding, have occurred in recent years.
A general object of the present invention is to provide a unique safety-release tension-applying mechanism adapted to be interpositioned between such a facebow and a headstrap or the like, and constructed to release the connection between these two devices under circumstances with the facebow pulled just a slight distance away from a patient's face.
Still another object of the invention is to provide such a mechanism which, while capable of releasing the connection between a facebow and a headstrap, etc., it is also capable of transmitting the desired normal range of orthodontic tension without releasing the connection.
A further object of the instant invention is to provide a mechanism of the type so far generally described which is not easily defeated or disabled by a patient, and which, when release occurs, is easily reassembled with a return to the proper orthodontic force.
According to a preferred embodiment of the invention, the proposed safety-release mechanism includes a pair of releasably interconnectable parts, one of which includes a pair of spaced opposed relatively movable fingers which act as an infinitely changeable tension-producing gripper, and the other of which includes a portion shaped releasably to be gripped by this gripper. As tension is transmitted through the mechanism increases, the two parts just mentioned therein tend to shift apart from one another, with gradual spreading of the fingers in the first mentioned part. Such fingers, therefore, function as active tension-applying elements in an overall assembly including a headstrap and the like and an orthodontic facebow. The parts in the mechanism continue to move apart with increased tension, as for example might be caused by someone pulling outwardly on a face bow, throughout a prescribed predetermined range of tensions, whereupon the two parts in the mechanism automatically and smoothly release. Nothing is built into the mechanism which tends to stop the gradual and progressive separation of the parts as such tension buildup occurs.
Another feature of the invention is that the two parts are constructed to engage in such a manner as to allow for relative rotation or pivoting about an axis substantially normal to that axis along which tension may be transmitted. This is an important feature in maximizing wearer comfort since it allows angulation to occur between a facebow and a headstrap so as to place both in the most advantageous and comfortable positions.
In most instances, a pair of mechanisms constructed in accordance with the invention will preferably be used, each being operatively interconnected between an end of a facebow and an end of a headstrap or the like. However, it is recognized that there are some applications in which but a single mechanism might be entirely satisfactory. Also, two different modifications of the invention, differing slightly in construction, are shown and described specifically herein. Other modifications are suggested by way of description.
As will become apparent from the description which follows, if a releasing action takes place, it is an extremely simple matter for a patient to reassemble the mechanism. Further, reassembly results in substantially exactly the same orthodontic force existing in the overall headgear as existed prior to release. Further, the modifications of the invention described herein are not placeable into use without the safety-release feature being automatically operative. In other words, it is not practically possible for a patient to defeat the safety-release feature.
As will also be explained below, the sizing of various parts used in the mechanism of the invention is a matter of choice, and can be used as a means for controlling the specific range of orthodontic tension forces which an orthodontist wishes to use. Thus, a relatively wide range of normal orthodontic forces may be applied through the mechanism. These and other objects and advantages attained by the invention will become more fully apparent as the description which now follows is read in conjunction with the accompanying drawings.